There are some obvious advantages to hi-beat movements (28,800 and faster) but wear and tear considerations are obviously not one of them, compared to the slower classic beat rates (18K/19.8K), which vintage Rolex have.

Watchmakers and horological gurus: how MUCH more wear does a hi-beat balance frequency exact on the mechanism overall, and who feels that the current crop of 28.8 vph calibers made by Rolex can hope to stand the test of time, assuming consistent servicing? Is the wear and stress the modern movements undergo considerably greater--or just somewhat more--than the vintage slow-beat examples?

Are slow beat movements really that much more tolerant of lax servicing over the years, or no?

It's interesting that virtually all the top independent guys have pretty much stuck with classic beat rates (18,000/19,800/21,600) etc for their hand crafted watches. I would assume that is because these are expected to be generational quality, so its food for thought. The same can be said for many of the haute horlogerie manufactures, although some--like PP--have began embracing modern beat rates for much of their production as well. You do hear from time to time that modern calibers are probably more advanced/efficient in DESIGN (due to the C.A.D. age, probably) but the older calibers exceed their modern counterparts in constructive, decorative and component quality.

I guess the nutshell of the questions is: Excluding some of the technical advantages that modern hi-beat calibers offer, would it be best to stick with a well constructed slow-beat caliber if the primary objective is having a watch last the longest possible time in good mechanical condition?

Great question. I have wondered about this as well. You may know that several Swiss companies worked together on a "hi beat" 36,000 beat per hour movement as the quartz watches were coming in back in the early 1970's. These had some reliability issues. It seems that the main issues with 28,800 bph and below are not serious, excepting no cleaning and oiling for more than 5 years or so. After that, the steel rotor axle can be an issue. Rolexes are tough and reliable with regular service, I think in the overall.

...if properly maintained and serviced as per Rolex instructions, there's no reason their high(er) beat movements shouldn't last as long as their low(er) beat movements.

Where things get sticky, is when an owner expects his watch to work perfectly, unserviced, for 25+ years because his old 15xx-powered Sub did. You're not likely to be as lucky with higher-beat calibres.